Enhance option suggestion for options expected an argument (PR driver/89861).

Enhance option suggestion for options expected an argument (PR driver/89861).

2019-04-01  Martin Liska  <mliska@suse.cz>

	PR driver/89861
	* opt-suggestions.c (option_proposer::build_option_suggestions):
	Add variant without any argument in order to provide better
	hints.
2019-04-01  Martin Liska  <mliska@suse.cz>

	PR driver/89861
	* gcc.dg/spellcheck-options-18.c: New test.
	* gcc.dg/spellcheck-options-19.c: New test.
	* gcc.dg/spellcheck-options-20.c: New test.
	* gcc.dg/spellcheck-options-13.c: Adjust expected output.
	* gcc.dg/completion-2.c: Add one variant with no argument.

From-SVN: r270053